1. Field of the Invention
The present invention is directed to a radiation diaphragm of the type having a diaphragm lamella engaged by an adjustment system, so that the lamella is adjustable in the ray beam of a radiation transmitter.
2. Description of the Prior Art
European Application 0 373 285 discloses a gating device for an x-ray diagnostics installation which includes a rigid element that is adjustable around a longitudinal axis in a plane perpendicular to the useful ray beam, and which has an arcuate edge. As a result of the variable arrangement of the arcuate edge, the useful ray beam can be individually matched to (gated onto) an arcuately shaped examination subject.
German OS 35 00 812 discloses a gating mechanism for x-radiation which includes rigid diaphragm lamellae adjustable into the ray beam, these lamellae lying against one another parallel to both sides of a slot, and being individually adjustable in the longitudinal direction by an adjustment system dependent on the size of a subject.
In angiographic examinations, for example of the legs of a patient, x-radiation is incident on regions of an image intensifier, used as the radiation receiver, which are not shadowed by the legs directly. Those regions may comprise a relatively large-area. The excessively high radiation intensity in these regions leads to a degradation of the image quality due to reduction of contrast and glare; moreover, the stray radiation is unnecessarily increased.
In order to counter these negative effects, diaphragms, for example of sheet lead, are employed, which are laterally moved into the beam path so that they are matched as well as possible to the contours of the examination subject. This gating is suitable in order to blank the ray beam at the sides of the legs. Strip-shaped diaphragms having a fixed shape that are arranged in the region between the legs are employed for blanking radiation that is incident on the image intensifier between the legs. It is also possible to provide plastically deformable and absorbent volumes, for example sacks of rice flour, in this region. This technique, however, is difficult to manipulate and increases the stray radiation.